When you add that index are more than 30% of the rows in the table DateTimeNext>1126215680?

Dan Baker wrote:

I have lots of tables that are similar in nature:

id int(11) PRI NULL auto_increment
Name varchar(30)
DateTimeNext int(11)

The "DateTimeNext" field represents when this records needs attention. A value of zero indicates it is being ignored. There are times when *lots* of records DateTimeNext values will be zero.

I want to find all records in the database that need attention today, so a typical query looks like:
SELECT id,Name FROM tbl WHERE DateTimeNext>1126215680

When I EXPLAIN this query, I get the following:
  table type possible_keys key key_len ref rows Extra
  Site, ALL, NULL,NULL, NULL, NULL, 53587,Using where

If I add an index for "DateTimeNext", the EXPLAIN shows:
  table type possible_keys key key_len ref rows Extra
  Site,ALL,DateTimeNext,NULL,NULL,NULL,53587,Using where

It appears that the index does NO good in this query.
Is there anything I can do to optimize this query? Alter the table to improve the query? Do anything to not scan the entire stinkin' table?

Thank you,
DanB






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